It is often desirable to use sport goggles, dive masks and other highly portable transparent eye-protecting shields in environments involving conditions which contribute to condensation build-up on the eye shield and where even momentary impairment of vision by fogging would be problematic. When the temperature of such an eye shield has dropped below a dew-point temperature, i.e., the atmospheric temperature below which water droplets begin to condense and dew can form, fogging has occurred.
A common characteristic of such portable eye-protecting shields is the fact that they are light weight enough to be worn on a user's head and are positioned relatively closely to a user's face such that the user's breath and body heat exacerbates fogging conditions. Examples of fog-prone sport goggles intended for use during winter activities, have included goggles for downhill skiing, cross-country skiing, snowboarding, snowmobiling, sledding, tubing, ice climbing and the like, and are widely known and widely utilized by sports enthusiasts and others whose duties or activities require them to be outside in snowy and other inclement cold weather conditions. Examples of fog-prone dive masks have included eye and nose masks independent of a breathing apparatus as well as full-face masks in which the breathing apparatus is integrated into the mask. Examples of fog-prone eye-protecting shields have included a face shield that a doctor or dentist would wear to prevent pathogens from getting into the user's mouth or eyes, or a transparent face shield portion of a motorcycle helmet. Fogging that impairs vision is a common problem with such goggles, dive masks and eye-protecting shields.
There have been various conductive apparatus devised for preventing condensation build-up on eye-shields for eye-protecting shields. The purpose of these conductive apparatus has been to provide an eye shield that may be maintained free of condensation so that the user would be able to enjoy unobstructed vision during viewing activities. Prior sports goggles with electronic systems have been primarily used in environments requiring a high degree of portability, that is, where a power source for powering the electronics for the device has been advantageously carried on a strap for the goggle or on the goggle itself as shown and described in co-pending U.S. Patent Application Ser. No. 61/563,738, by McCulloch, for Modular Anti-fog Goggle System. Such power source-powered devices, especially heating devices which consume extraordinary amounts of power from batteries, need to be judicious in the use of total available power source capacity, generally measured in amp-hours, to preserve power source life. Thus, the ability to adjust the amount of current delivered to the eye shield resistive element would have also been desirable.
A limitation of these devices has been that power source power that may be easily carried on one's person, for example on a head band or in a goggle or mask itself, in order to sustain longer-term use, has been limited. And while advancements in lithium-ion and related power source technologies have been made in recent years, it would nevertheless be desirable to improve upon the efficiency of eye shield heating systems in order to maximize power source life.
U.S. Pat. No. 4,868,929, to Curcio, for Electrically Heated Ski Goggles, comprises an eye shield with embedded resistive wires operatively connected via a switching device to an external power source pack adapted to produce heating of the eye shield for anti-fog purposes. U.S. Pat. No. 7,648,234, to Welchel et al., for Eyewear With Heating Elements, discloses use of nichrome and thin film heating elements used for heating an eye shield and discloses use of a control mechanism for turning on and off the heat to the eye shield.
Another problem with sport goggles which have employed electrical heating is that of uneven heating over the entire surface of the eye shield. Goggles and goggle eye-shields are manufactured with an irregular shape required to maintain a position close to the face of the wearer and allowing cutouts for the nose and extended edges for peripheral vision. Even heating of this irregular shape has not been accomplished in the prior art.
Prior art devices have been susceptible to hot spots, and using such devices in limited battery-powered applications has unduly discharged the battery. The reason for the hot spots has been because the electrical resistivity between the electrical connections across the resistive elements on the eye shield has been greater or lesser at different locations on the eye shield such that the amount of electrical current consumed in the areas with less distance between terminal connections is greater and the amount of electrical current consumed in areas with greater distance between the terminal connections is less. For example, where the terminals are on either side of the lens in a resistive wiring application, there have been problems with evenly heating the lens since the distance the wire has had to travel from one terminal to the other has been greater for those wires traveling over the bridge of the nose and down under the eyes than other wires that travel the shorter distance across a central portion of the lens. To overcome fogging conditions enough power must be applied to overcome the fog in the areas with the greatest distance between the terminal connection points, causing the smaller areas to overheat, which in turn wastes power. Thus, the problem has resulted in limited usefulness of heating of goggle eye-shields. Because of the irregular shape of eye shields, these problems exist whether one is considering resistive wire applications or resistive-film applications.
Still another problem associated particularly with goggles and dive masks is the amount of space provided between the eye shield portion of the device and the user's face. Where insufficient space has been provided, the wearing of corrective eye shield eye glasses within the goggle or mask has been prohibited. Further, where excess distance has been provided between the shield portion of the device and the user's eyes, the ability to incorporate corrective eye-shields into the goggle or mask eye shield itself has been prohibited. The problem has been, increased distance between the user's eyes and the eye shield has improved anti-fogging capability in typical air-flow dependent anti-fog goggles, however, locating the eye shield at such a great distance from the user's eyes to facilitate anti-fogging has made corrective goggle eye-shields less effective for correcting vision. Thus, what has been long needed in the corrective eye shield goggle, or dive mask, art is a technology that would both permit a corrective eye shield to be sufficiently close to the user's eyes to function properly from a vision correction perspective, but which is also capable of effective fog prevention.
Thus there has developed a need to provide a preferably automatically adjusting variable power source which can provide adequate current to meet the requirements of anti-fogging without presenting excessive power above that which is required. Also there has developed a need to provide multiple current supplies to multiple regions to enable even heating of goggle eye-shields across the entire eye shield surface without excessive use of power or hot-spots.
Switching the power on to a goggle when you experience fog conditions, and then switching it off when a user suspects it is no longer needed, is not an efficient way to overcome fog in a goggle or other vision shield. This is because while it is on, it is using full power and this is an inefficient use of battery resources. Also, the user doesn't really know precisely when to turn it off, so at best the user is guessing when is the best time to turn it off. Further, when a user is involved and concentrating on the activity at hand, it often is not convenient to have to turn on, or off, the power to the eye shield. Manual switching of power to an eye shield doesn't allow the user to set an intermediate heat value that is sufficient to curtail fogging but which also conserves battery life. Further, there are no known systems disclosed in the prior art for balanced heating of a film or other resistive element on an eye shield, such as goggles, glasses or sunglasses, which also provide variable control of a heating element on the eye shield.